Reaction injection molded (RIM) polyurethanes are well known in the art and have met with substantial commercial success. U.S. Pat. No. 4,218,543 describes the use of relatively high molecular weight hydroxyl group containing materials, certain aromatic diamines as chain extenders, and isocyanates for the production of RIM parts.
More recently the activity in the art has been towards the production of polyurea RIM parts. Typically, these parts are made from relatively high molecular weight polyethers which contain amine groups, diamine chain extenders and isocyanates. Typical of the materials used and the technologies known in the art are those described in U.S. Pat. Nos. 4,774,263, 4,774,264, 4,396,729, 4,433,067, 4,444,910 and 4,530,941. As is known in the art, RIM parts are generally produced from two separate streams. One stream generally contains the isocyanate component, while the other stream contains the amine-containing polyether and the amine chain extender. One problem is that blends of certain of the amine-containing polyether and the amine chain extender are generally too viscous for use in conventional commercial RIM machinery. An object of the present invention was therefore to provide a mixture of amine containing polyether and amine chain extender having a substantially reduced viscosity and thus improved flow characteristics. Additionally, this improvement in flow properties would have to be achieved without adversely affecting the physical properties of the final RIM part.
The use of cyclic alkylene carbonates in polyurethane chemistry is known. U.S. Pat. No. 3,883,466 describes the use of a cyclic alkylene carbonate as a liquid modifier to moderate the reaction exotherm between the hydroxy component and the polyisocyanate in the production of a rigid, dense rapid-setting polyurethane. U.S. Pat. Nos. 4,709,002 and 4,731,427 describe the use of cyclic alkylene carbonates in the production of rigid RIM polyisocyanurate and urethane-modified polyisocyanurate parts. These two references do not indicate why the cyclic alkylene carbonate is used but do suggest that the carbonate can be added to the isocyanate stream in order to reduce its viscosity.
U.S. Pat. Nos. 4,000,105 and 4,154,716 describe a variety of different liquid modifiers, including alkylene carbonates, which can be used in the production of rigid and non-elastomeric polyurethanes. The references do not indicate why the liquid modifiers are added. U.S. Pat. No. 4,530,941 suggests at column 7, lines 36-52, that the modifiers described in these two patents can be used in the production of polyurea RIM parts.